The production of modular timepiece sub-assemblies requires prefabrication to integrate adjustments which render the sub-assembly ready for use, and to avoid any further adjustments once the sub-assembly has been integrated in an assembly of higher rank.
In the particular case of a sub-assembly carrying a sprung balance assembly and an escape wheel, a known means of assembling a balance on a movement consists in pinning the sprung balance assembly up to a balance cock, and then adding this unit to a movement, pre-assembled with the escape wheel and the pallet lever. Once the balance-balance cock assembly has been mounted on the movement, a recurring difficulty arises as regards controlling the vertical shake of the balance between pivots on bearings or shock absorbers, which will be referred to in the description by the generic term “bearings”. To overcome this problem, systems of adjusting the balance shake are sometimes used.
If the overriding objective is to assemble the movement in an entirely automated and inexpensive manner, this method of pinning and assembling the balance on the movement is complex, since the process involves turning over the balance-balance cock assembly. Moreover, when the movement is being assembled, the balance remains suspended via the balance spring, which complicates handling.
The usual means of adjusting the balance shake generally comprises elements that are added, such as screws, nuts, springs, or suchlike, which can create an adjustment mechanically. The increase in the number of components linked to the presence of these adjusting means increases the price of the movement components and increases the number of assembly operations and thereby the total cost.
EP Patent Application No. 1804 142 A1 in the name of ETA SA and OMEGA SA discloses a device for adjusting the shake of a wheel set rotating between two bearings, one in a bridge and the other in a bottom roller. The means of adjustment includes an element for adjusting the distance between a base of the bridge and the bottom roller. The adjusting element has a first hole for a securing screw and can be activated through a second hole machined into the base and passing therethrough. The securing screw is inserted into the second hole to secure the base to the bottom roller, but is not in place in the second hole when the adjusting element is actuated from the top surface of the bridge opposite the bottom roller and through the second hole in order to adjust the shake of the rotating wheel set.
EP Patent Application No. 1804 143 A1 in the name of ETA SA and OMEGA SA discloses a means of adjustment for a similar rotating wheel set, formed, on the one hand, by a conventional means of securing a first portion of the bridge to the bottom roller leaving said first portion in a fixed position relative to the bottom roller and, on the other hand, by a means of deforming the bridge, which is arranged to vary the relative position between a second portion of the bridge and the bottom roller by deforming said bridge. These first and second portions of the bridge are arranged so that activating the bridge deforming means causes a variation in the distance between the first bearing and the second bearing.